Color control apparatus



W- 2 42 A. MK. GREAVES"W3%LRER 2,302,763

COLOR CONTROL APPARATUS Filed March 24, 3.939

Brwentor k&/ AKrHur? Ms ff. Gfimvw-Mmm gala/ Grim-neg Patented Nov. 24, 1942 COLOR CONTROL APPARATUS Arthur McK. Greaves-Walker, Toledo, Ohio, as-

signor to Libbey-Owens-Ford Glass Company, Toledo, Ohio, a corporation of Ohio Application March 24, 1939, Serial No. 264,026

2 Claims.

The present invention relates broadly to the art of decorating glass and more particularly to the surface coloring of glass sheets or plates.

When using colored glass sheets for any purpose where a plurality of sheets of the same color are required such as for facing the walls of bathrooms, kitchens, etc., it is obviously highly desirable that all of the sheets have exactly the same tone value or, in other words, that they accurately match one another to present a uniform, attractive surface. The necessity for accurate color matching of the glass sheets is especially important where the sheets are to be employed for luminous sign or architectural uses. That is to say, where the sheets are illuminated by lighting means arranged in back thereof. In such uses, any variation in the color between the glass sheets will be readily discernible.

In the surface coloring of glass sheets, the tone value or shading thereof depends largely upon the thickness of the layer of coloring material applied thereto. Therefore, in order to obtain exactly the same tone value upon successive sheets of glass 50 that they will accurately match one another, it is necessary that the color coats on all of the sheets be not only uniformly applied but also of the same thickness. This color matching of the glass sheets is not only essential in an initial installation where a plurality of sheets are used, but is equally important where replacements are required due to the break ng of one or more of the original sheets. Manifestly, the new sheet or sheets of glass should accurately match the original sheets so as not to spoil the appearance of the wall surface, luminous sign, or the like.

One of th major problems encountered in the use of surface colored glass sheets, particularly for luminous sign or structural work, has been this lack of uniformity of color and the difiiculty experienced in consistently duplicating a given number of sheets having the same tone value. This has been due mainly to the fact that it has been heretofore necessary to depend entirely upon the skill o the operator, applying the coloring material to the glass sheet, to determine when the color coat is of the proper thickness to give the desired tone value or shading. This has, however, constituted a more or less hit and miss method and is attendant with obvious objections. t

It is an aim of this invention to provide, in the surface coloring of glass sheets or plates, a positive and accurate control for measuring the thickness of the color coat upon the sheet, thereby rendering possible the consistent duplication of any desired number of sheets having equal tone values.

- Another object of the invention is the provision of a novel apparatus for determining the tone value of the colored glass sheet by registering or otherwise indicating the intensity of light passed through the sheet after the coloring material has been applied thereto.

Briefly stated, in carrying out the invention, the glass sheet tobe colored is preferably. suspended or otherwise suitably supported in a vertical or substantially vertical position in front of a lighted background. A light sensitive device including a photoelectric cell is positioned in back of the glass sheet and is connected with a suitable measuring or indicating instrument, such as a potentiometer. The coloring material is then applied to the front surface of the sheet preferably by spraying the same thereon, and when the operator feels that a color coat of the desired thickness has been applied to the glass, he extinguishes the lighted background and turns on one or more electric lamps arranged in front of the sheet. The rays of light from these lamps are projected rcarwardl through the glass sheet upon the light sensitive device to cause the actuation thereof.

When the light sensitive device is thus exposed to light, the photoelectric cell develops sufficient current to operate the indicating instrument whch measures the intensity of the light passed through the glass sheet and impinging upon the light sensitive device. The reading given by the indicating instrument will then inform the operator whether or not the color coat upon the sheet is of the proper thickness to give a sheet having the desired tone value. The intensity of the light impinging upon the photoelectric cell depends upon the drgree of transparency or translucency of the glass sheet which is in turn determined by the amount of coloring material applied thereto. The operator may. of course, take one or more read ngs during the spraying of the coloring material until the measuring instrument indicates that the proper amount of coloring material has been applied to the glass to give the desired tone value. The proper reading will of course be first determined, with different readings for different colors and tone values.

O'her objects and advantages of the invention will become more apparent during the course of the following description, when taken in conneclion wi'h the accompanying drawing.

In the drawing, wherein like numerals are employed to designate like parts throughout the same:

Fig. 1 is a vertical longitudinal section through apparatus provided in accordance with the invention; and

Fig. 2 is a diagrammatic front view of the apparatus showing the electrical control for the several light sensitive devices.

With reference particularly to the drawing, the glass sheet In to be colored is suspended in a vertical position from a plurality of relatively small hooks or tongs engaging opposite surfaces of the sheet adjacent its upper edge. The hooks or tongs are hung from a carriage |2 having rollers l3 which run along a monorail l4 by means of which the glass sheet may be moved into position for coloring and out of position after coloring.

The coloring of the glass sheet is preferably performed in a spray booth l5 having a horizontal top wall I6, a vertical rear wall, and opposite vertical sid walls the spray booth is a frame 2|) carrying a plurality of electric lamps 24 which are adapted to illuminate the spray booth and the glass sheet during the application of the coloring material to said sheet.

Positioned within the spray booth I5 is a vertical supporting standard 46 upon which is slidably mounted a bearing 41 through which passes a horizontal rod 48, said bearing 41 being secured in place upon standard 46 by a set screw the forward end.

or the like 49. Mounted upon of the rod 49 are a vided intermediate and 53 respectively,

pair of arms 50 and 5| prowhich are rotatably received upon the said rod-49'z and secured in desired position thereon by set screws or the like 54 and 55.

Carried by the arm 50 are the light sensitive devices 56 and 51, while similar light sensitive devices 56 and 59 are mounted upon arm 5|. A light sensitive device 60 is also secured to the forward end of the rod 48. Each of these light sensitive devices may contain one or more photoelectric cells. Each of the light sensitive devices 56, 51, 58, and 59 is carried by a support 6| slidable upon the respective supporting arm 5|! or 5| and secured thereto by like 62;

All of the light sensitive devices 56 to 60 inclusive are connected with a common indicating instrument or potentiometer 63 through a control switch 64. This switch is provided with a plurality of contacts 65 to 69 inclusive and also with a rotatable contact arm adapted for selective engagement with said contacts 65 to 69. Leading from each of thelight sensitive devices to one of the contacts of the switch 64 is a wire while also running from each of the light sensitive devices to the terminal 12 of the indicating instrument 63 is a wire 13. The rotatable contact arm 10 of switch 64 is connected with the terminal of the indicating instrument by a wire 14.

Upon turning of the rotatable contact arm 10 of switch 64 to engage any one of the contacts 65 to 69, a circuit will be completed through the respective light sensitive device with which the said contact is connected. In this way, it is possible for the operator, upon turning of the contact arm 19, to connect any one of the light sensitive devices 56 to 60 with the indicating instrument 63 so that the indicating instrument will measure the intensity of the light projected through the glass sheet and impinging upon the respective light sensitive device. By providing a plurality of light sensitive devices, the intensity a set screw or the IB. Secured to the back wall of their ends with bearings 52V of. the light passing through the glass sheet can be measured at a plurality of different points onthe sheet so as to give a more comprehensive measurement of the thickness of the color coat applied to the glass. The light sensitive devices 56, 51, 58, and 59 can be moved along the supporting arms 50 and 5| and likewise the supporting arms can be swung to either a substantially vertical position or to a substantially horizontal position to take care of sheets of different sizes and shapes.

In practice, the light sensitive devices 56 to 56 inclusive are positioned behind the glass sheet In to be colored in the manner shown in Fig. 1, while the coloring material is applied to the front surface of the sheet preferably by means of a spray gun 11. During the application of the coloring material to the glass sheet, the electric lamps 24 are lighted. However, when the operator feels that the proper amount of coloring material has been applied to the glass he switches off the lamps 24 and turns on a suitable source of light at the front of the sheet. This source of light may comprise a casing 18 positioned directly in front of the glass sheet, but spaced a suitable distance therefrom, and containing a plurality of electric lamps 19. The front of the casing 18 is covered by a light diffusing plate which serves to distribute the light from the lamps l9 uniformly over the glass sheet.

The light from the electric lamps I9 is projected through the glass sheet l0 and impinges upon the light sensitive devices 56 to 60 inclusive. By turning the rotatable contact arm 1|) of switch 64 to engage contacts 65 to 69 inclusive, the operator can place the light sensitive devices one at a time in circuit with the indicating instrument 63 to measure the thickness of the layer of coloring material upon the glass sheet at a plurality of points.

Although the invention is not limited to the use of any particular type of coloring material, it preferably consists of a frit enamel formed of vitrifiable materials including as one of its components pulverized or powdered glass suspended in a liquid vehicle to form a solution of the desired consistency. The glass used in making the enamel is frequently of lead borosilicate, or lead borate glass, although other types of glass of equal low fusing temperature may be employed. The liquid vehicle may consist of a highly volatile composition, such as a mixture of alcohol and water, or oil types of vehicles, such as turpentine and other oily materials may be used. The glass frit is finely ground, such as in a ball mill, and is preferably sufficiently fine to pass through a 200 mesh screen. The enamel solution containing the vitrifiable colors can be applied to the glass sheet in any desired manner, but as stated above is preferably sprayed thereon.

While it is preferred that the glass sheet be suspended in a vertical position, as shown, during the application of the coloring material thereto, it can of course be arranged horizontally if desired. Also, instead of suspending the sheet from a plurality of tongs, it may be mounted during spraying upon a suitable easel or rack.

When the sheet has been properly coated, it is adapted to be heated within a suitable furnace or been fired upon the be annealed by a slow and gradual cooling or, if preferred, it can be tempered by subjecting it to a sudden cooling or chilling treatment. When it is desired to temper the glass, the coated sheet is heated during the firing of the coloring material thereon to approximately the point of softening of the glass and then suddenly chilled to place the outer surfaces of the sheet under compression and its interior under tension.

Any well known method and apparatus can be employed for tempering the glass sheet, such as, for example, that disclosed in Patent 2,068,746, issued January 26, 1937. When tempering the glass sheet, the coloring material used is preferably of such composition and of such character that the time and temperature required for properly firing the same upon the glass will be the same as the time and temperature required for heating the sheet preliminary to cooling. Further, the coloring material is preferably of such composition and of such character that after being fired upon the glass it possesses the same coefllcient of expansion and contraction as the glass. By employing a coloring material of this type, the tempering and coloring operations can be performed simultaneously without either adversely affecting or in any way proving detrimental to the other. Also, due to the fact that the coloring material and glass have the same coefllcient of expansion and contraction, the liability of the coloring material separating from the glass during the varying temperature conditions to which it is subjected when in use will be eliminated.

Although there has been described hereinabove the application of coloring material to only one side of the glass sheet, it will be appreciated that the invention also contemplates the coloring of both surfaces thereof. For example, in the making of luminous signs, the letter colors can be applied to one surface of the glass and the background or field color applied to the opposite side. The letter colors would ordinarily be applied first and the field color second. The tone value of the colored letters could be controlled in the manner set forth above and, when applying the field color, one or more light sensitive devices could be arranged in back of the sheet between the letters.

It is to be understood that the form of the invention herewith shown and described is to be taken as the preferred embodiment of the same, and that various changes in the shape, size and arrangement of parts may be resorted to without departing from the spirit of the invention or the scope of the subjoined claims.

I claim:

1. Means for determining the tone value of colored glass sheets and the like, comprising means for supporting the sheet, a source of light arranged at one side of the sheet for directing light therethrough, a pair of supporting members arranged at the opposite side of the sheet extending in planes substantially parallel with the plane of said sheet, a plurality of light sensitive devices slidably carried upon each supporting member, means for mounting said supporting members intermediate their ends for rotatable movement relative to extending substantially perpendicular with respect to the plane of said sheet, and an indicating instrument associated with said light sensitive devices for measuring the intensity of the light passed through the colored sheet and impinging upon the said light sensitive devices.

2. Means for determining the tone value of colored glass sheets and the like, comprising means for supporting the sheet, a source of light arranged at one side of the sheet for directing light therethrough, a pair of supporting members arranged at the opposite side of the sheet extending in planes substantially parallel with the plane of said sheet, a plurality of light sensitive devices slidably carried upon each supporting member, means for mounting said supporting members intermediate their ends for rotatable movement relative to one another about an axis extending substantially perpendicular with respect to the plane of said sheet, an indicating instrument, and a control switch connected in circuit with said light sensitive devices and indicating instrument and operable to complete a circuit through the said indicating instrument and light sensitive devices selectively whereby the intensity of the light passing through the sheet can be measured at a plurality of different points.

ARTHUR McK. GREAVES-WALKER.

one another about an axis 

